Electrical circuitry often must be protected from disruptions caused by electromagnetic interference (EMI) and radio frequency interference (RFI) entering the system.
Frequently today's electronic circuitry requires the use of high density, multiple contact electrical connectors. There are many applications in which it is desirable to provide a connector with a filtering capability, for example, to suppress EMI and RFI. To retain the convenience and flexibility of the connector, however, it is desirable that the filtering capability be incorporated into connectors in a manner that will permit full interchangability between the filtered connectors and their unfiltered counterparts. In particular, any filtered connector should also in many instances retain substantially the same dimensions as the unfiltered version and should have the same contact arrangement so that either can be connected to an appropriate mating connector.
One means to protect against undesirable interference without altering the internal structure of a connector is by the use of shielding. The shielding may take several forms. For adequate protection, it is essential, however, that there be no break in continuity of the shielding. In some instances, it is desirable to provide a combination of shielding and filtering. For ease of manufacturing assembly it is also desirable to provide filtering capability with a minimum number of parts. One way to achieve this result is to use thick film capacitors such as those described in U.S. Pat. Nos. 4,682,129 and 4,791,391. These capacitors are formed on electrically inert substrates. The insertion loss obtainable with these devices depends, therefore, solely on the value of the capacitors. For some applications, these capacitor devices can not achieve the desired insertion loss. It is desirable, therefore, to have a planar filter construction that meets industry demands for filtered connectors having higher insertion loss.